The oldest sewers across the nation are often non-circular as for example, elliptical, horse shoe or parabolic, in cross-sectional shape. Such sewer lines are in need of repair and/or rehabilitation, but normally cannot be taken out of service during the rehabilitation effort because they are both large in diameter, and critical to the overall capacity of the city's sewer system. One approach to repairing these sewer lines would be by using by-pass lines. However, such by-pass lines would be large, affect traffic at street level and thus be impractical for these larger diameter sewers.
An alternative approach to repairing such large non-circular sewer pipelines is by relining them in a “live” condition by jacking relining pipe sections into the sewer pipeline. This process is known as slip lining. This is accomplished by cutting a top portion of a pipe in the sewer pipeline inserting in a relining pipe section and pushing (i.e., jacking) the relining pipe section forward in the sewer pipeline. The lining pipe is pushed further forward as a new lining pipe section is inserted and pushed forward in the sewer pipeline section. However, the approach of slip lining is not without its problems, as the jacking loads that are used for installing the new lining pipe section into position can be very high, and can result in damage to the ends of the lining pipe section.
Conventional pipe sections used for slip lining sewer pipes in this manner are not configured having a non-circular cross-section, but rather are configured having a circular cross-section. An example of such slip lining pipe is one available from HOBAS Engineering AG, Houston, Tex. The use of such conventional slip lining pipe (having a circular cross-section) to repair an elliptical sewer pipe, for example, results in a reduced effective fluid transport passage, thereby providing a significant reduction or loss of fluid transport capacity. This loss of capacity is often too high relative to the city's needs. For example, the use of such conventional slip lining pipe to repair a typical 73 inch×60 inch elliptical sewer pipe reduces the sewer pipe capacity from approximately 90 cfs to 50 cfs, i.e., producing a 44 percent reduction of capacity.
Moreover, conventional slip pipe sections, such as the HOBAS pipes are manufactured using a spinning process. As such these pipes have a resin rich inner surface for providing necessary corrosion protection on the inside of the pipe. However, the ends of the HOBAS pipes are saw cut and expose sand filler and chopped fiber that make up the pipes' structural walls. These cut ends are exposed to the sewer gases that can cause rapid deterioration of the pipe ends forming the pipeline.
Other lining pipe sections currently used such as the Spiro Lite pipe made by Chevron have external circumferential ribs for stiffening the lining pipe. These ribs are rounded in cross-section and tend to mechanically lock on the imperfections inside the host sewer pipeline preventing the insertion of the lining pipe in the sewer pipeline.
It is, therefore, desired that a pipe section be constructed for elliptical sewer pipelines by slip lining in a manner that does not produce a large reduction of fluid transport capacity. It is also desired that the pipe section comprise joints at the ends that are self sealing, capable of withstanding the jacking loads, and that are corrosion resistant to the sulfuric acid attack typically found inside a sewer line (pH=1). Moreover a lining pipe is desired that does not mechanically lock with the imperfections inside the sewer pipeline as it is being inserted in the sewer pipeline.